Avalanche forecast

North Columbia

Mar 28 – 29, 2017Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Forecast precipitation, wind and warming is expected to keep the avalanche danger elevated. Conservative route selection and terrain use is warranted during these conditions.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    Recent wind from the SW has redistributed the new storm snow in exposed terrain at higher elevations forming reactive wind slabs. Cornices are large and may become weak with daytime warming, sun exposure, or during stormy periods.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    A cornice fall or smaller slab avalanches could trigger deep, destructive avalanches on buried weak layers. There is a low likelihood of triggering but a high consequence if triggered. These avalanches would likely run full path.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Warmer temperatures and rain will deteriorate the lower elevation snowpack, initiating loose wet avalanches that may slide easily on a buried crust.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A series of low pressure systems will sweep across the Interior tonight through tomorrow bringing precipitation and light-moderate winds. A clearing trend with an associated ridge will start to set up later Thursday into Friday. Wednesday: Snow amounts 5-10 cm by the am with an additional 5-10 cm through the day. Ridgetop winds will be moderate from the West and freezing levels near 1500 m. Thursday: Mostly cloudy with possible sunny breaks. Ridgetop winds light-moderate from the NW. Alpine temperatures near -7 and freezing levels 1500 m. Friday: Sunny with some high cloud. Alpine temperatures high of -2 and freezing levels 1700 m.

Avalanche Summary

On Monday, storm slabs and wind slabs up to size 2 were observed and continue to be reactive to rider triggers. Loose wet activity up to size 1 was reported from south facing terrain. With continued precipitation and wind, natural avalanche activity will likely continue. Fragile cornices are also suspect, they are large enough and act as heavy triggers for deeper slab avalanches to release on the slopes below. If you're traveling below treeline where the avalanche hazard is lower than it is in the alpine you should remain diligent with your terrain use, mitigate overhead hazards by avoiding or lingering in run-out zones where large avalanches could come down from above. We remain in a low probability, high consequence scenario for persistent slab avalanches failing on deeply buried weak layers. Check out the recent Forecaster Blogs for more details.

Snowpack Summary

Up to 20 cm of new storm snow has fallen at upper elevations. This now brings 30-70 cm of accumulated snow over the past week which overlies the mid-March rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At lower elevations, there may be multiple crust layers in the upper snowpack which are now generally well bonded. At higher elevations, the February weak layers are down 120-150 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches.

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